The present invention relates to a shield-shaped or frame-shaped walking mine roof support. More particularly, it relates to a mine support which has a roof engaging cap element, two supporting units each including a floor engaging plate member and a prop extending between a respective one of the plate members and the roof supporting cap element so as to support the latter, and displacing means for displacing the floor engaging plate members.
Shield-shaped roof supports and supporting frames with one piece roof engaging cap element and two floor engaging plate members movable independently of one another, particularly in a vertical direction, have been proposed in the art. The roof engaging cap elements have in many cases large surfaces and their width corresponds to the length of the individual segments of a conveyor for transporting removed material, which conveyor can form an abutment element for the supports. The length of the individual segments usually corresponds to 1.50 meters. A guiding element is located between the floor engaging plate members. A mine face end portion of the guiding element is articulately connected with the conveyor, whereas its other end portion is connected with the backwardly directed end section of a (usually hydraulically operated) cylinder-piston unit. The front end section of the cylinder-piston unit is fixed to a bridge, which is connected with the mine face end sections of the floor engaging plate members and thereby transversely overlies the guiding element. Preferably, the piston rod of the cylinder-piston unit is connected with the rearward end section of the guiding element, whereas the cylinder of the cylinder-piston unit is connected with the bridge. In this case, the large surface of the piston can be used for simultaneous displacement of both floor engaging plate members, i.e., for displacement of the shield-shaped supports or the supporting frames, and the small annular surface in the piston rod space can be used for displacement of the conveyor. The respective supporting units to be moved, on the one hand, and the conveyor together with the supporting unit fixed thereto, on the other hand, thus each alternately form an abutment for the other, in the case of advancement or pulling of the respective elements.
This arrangement and manner of operation has the advantage that during the advancement of the roof support, due to the large surface of the roof supporting cap element and the supporting force which is necessarily reduced during such advancement when the surface is disengaged, a relatively large roof area is temporarily not supported or supported only with such a supporting force which just permits a displacement of the roof support. The locally reduced support of the rock, especially in the case of very unstable roof rocks, makes it impossible to categorically prevent breaking or flowing of the roof rock under these circumstances,
It has been further proposed to combine two shield-shaped supports or two supporting frames into one supporting unit and to provide displacing means therebetween. Such a support unit can walk and perform forward and backward movements fully independent of the mine-face removal operation, i.e., that is of the conveyor advancing motion. This independence of the supporting unit from the conveyor is of advantage, e.g., when kinks occur during the advancement when and due to this, the position of a given supporting unit cannot, or only by special labor-intensive step, be accommodated to the (now curved or kinked) shape of the articulated conveyor. However, in this case special conveyor-moving devices are necessary, which increase the apparatus expenditures for the arrangement. Furthermore, such support units, whether constructed as a shield-shaped support or a supporting frame, have the same large-surface roof engaging cap as the first-mentioned arrangement, wherein the supporting units are articulately connected with the conveyor through the guiding element. Since the width of a support or a supporting frame is in practice usually equal to about 1.50 meter in order to correspond to the length of the segments of the conveyor, this means that even in self-advancing shield-shaped supports or supporting frames large roof areas are sometimes not or not sufficiently supported during displacement of these units. Layers of rock which tends to break or to flow therefore require the use of special methods which naturally require higher expenditures of material and larger numbers of miners.